In a typical VF tube, and anode and grid voltage is required to provide the accelerating potential for electrons, emitted from a heated filament, to strike a fluorescent material and cause light emission. The light intensity depends upon the accelerating potential which is a function of both filament-to-anode voltage and grid-to-anode voltage. In automotive vehicle use, for example, battery voltage is subject to variation over a range so that if the anode and grid voltage were allowed to vary with the battery voltage the accelerating potential and thus the light intensity would vary considerably. In many applications, the anode and grid voltages (which may be the same) are derived from a switching power supply or other means to boost and regulate the anode and grid voltages at the proper level. Maintaining a regulated voltage to the grids and anodes eliminates variations in emitted light intensity of the VF tube due to applied input voltage.
The drawback of converting battery voltage to a regulated voltage is the inefficiency of the regulator. Depending on the type of regulator, efficiency is typically 65 to 80%. The remainder is converted to heat which, in some cases requires a heat sink for thermal dissipation. If it were possible to sufficiently reduce the power conversion requirements, then the heat sink would be unnecessary in some cases. Such reduction may also allow the use of smaller power supply.